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WOS: 000526980900010, A two-step Thermo reactive diffusion processes (including an initial titatinizing step followed by boronizing) is proposed in order to obtain superhard complex TiBC coating layer on AISI D6 steel. Microstructural characterization and mechanical properties of obtained TiBC layer conducted by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), optical microscopy, 2D profilometer, X-ray diffraction (XRD), micro-hardness, nano-indentation hardness and ball-on disc wear tests. Wear tests were carried out in ball on disc device by applying 30 N load and 500 m sliding distance against WC abrasive ball. Microstructural studies revealed a compact, homogenous and crack-free TiBC layer with 0.29-1.91 surface roughness (Ra), 3.65-29.5 mu m thickness and 1800-4841 HV0.05, hardness and 146-235 GPa elastic modulus. Hardness values of TiBC layers was significantly higher than those obtained by standard titanizing and boronizing due to the interspersed TiB and TiC phases within the TiBC layer. Higher hardness values are highly effective on the wear resistance and wear type. Thus, in parallel with the increase in mechanical properties, wear resistance increased in the range of 4-120 times in comparison with the untreated AISI D6 sample. Severe wear and extensive plastic deformation was observed in the untreated AISI D6, while micro-cutting, micro-cracking and pitting was dominant in samples with hardness 1800-4000 HV. When the surface hardness reached values above 4000 HV the wear mechanism further changed to microcracking and spalling.

Porous NiTi shape memory alloy (SMA) was fabricated by self-propagating high-temperature synthesis (SHS). With this study, a new solution treatment “solution treatment under loading” was applied to porous NiTi SMA fabricated by SHS to determine microstructural improvement regarding single phase NiTi. The effect of solution treatment under load on chemical composition, constituent phases and phase transformation behaviors of the specimens was investigated and discussed. The chemical composition of the specimens considerably changed with solution treatment under loading. Intermetallic phases such as Ti 2 Ni and Ni 4 Ti 3 disappeared, the density of B2(NiTi) phase increased and phase transformation temperatures sharply decreased. Porous single phase B2(NiTi) SMA with high chemical homogeneity could be obtained by the load applied during solution treatment at 1050 °C.

In this study, a martensitic stainless steel plate of 10 mm thick was welded by keyhole plasma transfer arc (PTA) welding technique both itself and using austenitic stainless steel plate of 2 mm thick in interface. So, penetration depth, microstructure, mechanical behavior and interface layer effects of keyhole plasma welding were investigated. After keyhole plasma welding, microstructural analysis including metallographic examination, and notch impact strength tests were performed. From the results, it was seen that with this technique can be obtained penetration depth of 8 mm without any pretreatment of welding. Also, austenitic stainless steel interface layer was raised impact strength of welding.

In this study, NiTi powder mixture was coated on the surface of an austenitic stainless steel (AISI 304) by plasma transferred arc (PTA). Coating was carried out by using 80, 90, 100 A current density under Ar atmosphere. Coating layer and interface were examined with SEM, EDX, XRD analysis and micro hardness test. Thickness of coating increased with current density. No cracks or pores were detected in the interface. Higher arc current densities caused a coating layer poor in NiTi alloy. Secondary phases such as Cr 2 Fe 7 Ni, Fe 7 Cr 2 Ni and Ni 3 Ti also formed in the coating layer.

In the present study, a duplex stainless steel and an austenitic stainless steel were diffusion bonded to medium carbon steel. The differences of two dissimilar metal couples at the test temperature on microstructural developments across the joint region were investigated. After diffusion bonding, microstructural analysis including metallographic examination, energy dispersive spectroscopy (EDS) and shear strength tests were performed. From the results, it was seen that mutual diffusion of C and Cr was effective on the morphology of the diffusion zone that affected the shear strength of the bonds.

In the present study, Ti-6Al-4V alloy was diffusion bonded to a ferritic stainless steel. The effect of bonding temperature on the microstructural development across the joint region was investigated. After diffusion bonding, microstructural analysis including metallographic examination, energy dispersive spectrograph (EDS) and shear strength was conduced. From the results, it was seen that bonding on the temperature was affecting the Fe and Ti mutual diffusion which controls the interface microstructure. The microstructure of the interface region was formed, consisting of Fe and Ti intermetallics. (c) 2006 Elsevier B.V. All rights reserved.

In the present study, a gray cast iron and a medium carbon steel couple were diffusion bonded at the temperatures of 850, 900, 950 and 1000 °C under a pressure of 8 MPa for 30 min, and the effects of temperature and high heating and cooling rate on interface formations and microstructure were investigated. After diffusion bonding, scanning electron microscopy, shear test measurements and microhardness measurement of interface region were made. The microstructure at the inside of medium carbon steel of bonded couple consisted of martensite. As a result, from the microstructural observations, a good bonding along the interface of the bonded couples and the interface is free from voids and microcracks.

In this study, the superplasticity of a hypoeutectoid carbon steel with 0.7% C was investigated considering Al and Si contents. The hot-tension experiments (superplasticity experiments) were carried out at 650 and 730 °C with the deformation rates between 3.3×10−4 and 1.3×10−2 s−1. The results showed that the best superplasticity elongation of 290% was achieved with the specimen containing 0.6% Si. The maximum m-values were determined as 0.29 at the test temperature of 650 °C and in the deformation rate range of 1×10−3 to 1.3×10−2 s−1 in the specimen with 0.6% Si content and 0.53 at the test temperature of 730 °C and the deformation rate range of 1×10−3 to 1.3×10−2 s−1 in the specimen with 0.15% Al content.